CN114853400A - Carbon black-carbon fiber composite wave-absorbing foam concrete and preparation method thereof - Google Patents
Carbon black-carbon fiber composite wave-absorbing foam concrete and preparation method thereof Download PDFInfo
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- CN114853400A CN114853400A CN202210392830.8A CN202210392830A CN114853400A CN 114853400 A CN114853400 A CN 114853400A CN 202210392830 A CN202210392830 A CN 202210392830A CN 114853400 A CN114853400 A CN 114853400A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
- C04B38/10—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by using foaming agents or by using mechanical means, e.g. adding preformed foam
- C04B38/106—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by using foaming agents or by using mechanical means, e.g. adding preformed foam by adding preformed foams
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00241—Physical properties of the materials not provided for elsewhere in C04B2111/00
- C04B2111/00258—Electromagnetic wave absorbing or shielding materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/40—Porous or lightweight materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/90—Electrical properties
- C04B2111/94—Electrically conducting materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
The invention belongs to the field of functional materials, and particularly discloses carbon black-carbon fiber composite wave-absorbing foam concrete and a preparation method thereof. The concrete of the invention is prepared by mixing wave-absorbing material and physical foaming agent, and the wet density is (900 +/-90) g/cm 3 Further curing the slurry to obtain the slurry; the wave-absorbing material is prepared from the following raw materials: ash, additive and water; wherein the ash body consists of cement, silica fume and nano carbon black; the additive is composed of methyl cellulose, a polycarboxylic acid water reducing agent and carbon fibers; the wave-absorbing material comprises the following components in parts by weight: cement accounts for 96wt% of the ash body, silica fume accounts for 3wt% of the ash body, and nano carbon black accounts for 1wt% of the ash body; the methylcellulose accounts for 0.3wt% of the ash, and the polycarboxylate superplasticizer accounts for1.0wt% of ash body, 0.25wt% to 1.5wt% of carbon fiber in the ash body, and 0.5 water-cement ratio. According to the invention, the foam concrete is prepared by mixing the nano carbon black and the carbon fiber material, so that the self weight is reduced, the impedance matching problem between the material and the free space is effectively solved, and the incidence possibility of electromagnetic waves is increased.
Description
Technical Field
The invention belongs to the field of functional materials, and particularly relates to carbon black-carbon fiber composite wave-absorbing foam concrete and a preparation method thereof.
Background
At the present stage, electronic science and technology are rapidly developed, pollution caused by electromagnetic radiation gradually causes adverse effects on life, for example, mutual interference among electromagnetic waves not only influences normal operation of equipment, but also causes obvious harm to human bodies caused by electromagnetic radiation, so that research on electromagnetic absorption materials is indispensable. The cement-based porous material is light in weight, has inherent advantages in matching wave-absorbing characteristics, and can avoid the characteristics of easy oxidation, easy falling and poor durability of the traditional wave-absorbing material. At present, the research on the cement-based wave-absorbing material mainly focuses on adding a wave-absorbing agent into the cement-based material to improve the electromagnetic performance and impedance matching of the whole material. The foam concrete contains a large number of closed and open holes, and is used as one of porous materials, electromagnetic waves are easy to continuously reflect and scatter in the holes so as to be attenuated, and the wave absorbing agent is added into the foam concrete, and the porous structure of the foam concrete can enable the foam concrete to have the heat preservation and wave absorbing functions at the same time, so that the multifunctional integration of building materials is realized.
The nano carbon black has lower cost and excellent environmental stability, can greatly improve the strength of foam concrete when being used as a wave absorbing agent, but has limited conductivity increase degree on a composite material when being singly doped, thereby influencing the absorption and loss effects of electromagnetic waves. The single doping of a wave absorbing agent is difficult to achieve the goal of high efficiency and broadband absorption, and the complex doping method is an effective way for widening the absorption frequency bandwidth. The prior art discloses that carbon black and carbon fiber composite doping is used as a wave-absorbing material, but the requirements of foam concrete on the fluidity and viscoplasticity of slurry are too high, and the method for successfully preparing the carbon black and carbon fiber composite wave-absorbing foam concrete is still deficient in the prior art.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide carbon black-carbon fiber composite wave-absorbing foam concrete and a preparation method thereof. The method of the invention directly utilizes the concrete material at the body side, and selects the porous material to solve the problem of poor impedance matching of the concrete, and effectively enhances the electromagnetic absorption and loss capacity of the composite material by doping the conductive particles.
In order to achieve the purpose, the invention adopts the following technical scheme:
a carbon black-carbon fiber composite wave-absorbing foam concrete is prepared by mixing a wave-absorbing material and a foaming agent.
The wave-absorbing material is prepared from the following raw materials: ash body, additive and water. Wherein the ash body consists of cement, silica fume and nano carbon black; the additive is composed of methyl cellulose, a polycarboxylic acid water reducing agent and carbon fibers.
The wave-absorbing material comprises the following components in parts by weight: cement accounts for 96wt% of the ash body, silica fume accounts for 3wt% of the ash body, and nano carbon black accounts for 1wt% of the ash body; the methyl cellulose accounts for 0.3wt% of the ash body, the polycarboxylate water reducing agent accounts for 1.0wt% of the ash body, the carbon fiber accounts for 0.25wt% -1.5 wt% of the ash body, and the water-cement ratio is 0.5.
Preferably, the carbon fiber accounts for 0.75wt% -1.5 wt% of the ash body.
Preferably, the carbon fibers account for 0.75wt% to 1.0wt% of the soot body.
Most preferably, the carbon fibers comprise 0.75wt% of the soot body.
The foaming agent is a physical foaming agent.
Further, the foaming agent is an HTW-1 type composite foaming agent.
Further, the nano carbon black: the grain diameter is less than or equal to 40 nm.
Further, the carbon fiber is chopped carbon fiber, the length of the carbon fiber is 0.7-1.5mm, and the diameter of the carbon fiber is 5-8 μm.
Preferably, the carbon fibers are chopped carbon fibers, and the carbon fibers have the length of 1mm and the diameter of 7 microns.
Further, the cement is quick-setting and quick-hardening sulphoaluminate cement.
Further, SiO in the silica fume 2 ≥98％。
Further, the methylcellulose is hydroxypropyl methylcellulose.
Further, the water reducing rate of the polycarboxylate superplasticizer is more than or equal to 25%.
The preparation method of the carbon black-carbon fiber composite wave-absorbing foam concrete comprises the following steps:
(1) weighing foaming agent, weighing the required water according to the corresponding dilution times, and uniformly stirring to obtain foaming agent solution;
(2) respectively weighing cement, nano carbon black and a polycarboxylate superplasticizer, putting the materials into a self-sealing bag, sealing and shaking up, namely performing pre-physical dispersion;
(3) weighing silica fume and carbon fiber, putting into a stirring pot, slowly stirring for 2-3 min by using a stirrer, and performing pre-physical dispersion;
(4) pouring all the dry powder in the step (2) into the stirring pot in the step (3), and slowly stirring for 2-3 min;
(5) weighing methyl cellulose and water, mixing the methyl cellulose and the water, quickly stirring for 1min to obtain a methyl cellulose solution, pouring the obtained methyl cellulose solution into the stirring pot in the step (4), slowly stirring for 2-3 min, and quickly stirring for 2-3 min; foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, taking foam, quickly adding the foam into a stirring pot, and uniformly stirring to ensure that the wet density of the slurry is (900 +/-90) g/cm 3 ；
(6) Pouring the fresh slurry obtained in the step (5) into a mold for molding, placing the mold into a standard curing room for curing for 16-24h, taking out the mold for demolding, and continuing placing the mold into the standard curing room for curing to the applicable age.
Further, the foaming agent in the step (1) is an HTW-1 type composite foaming agent, and the dilution ratio is 40 times.
Further, the wet density of the slurry is tested in step (5) according to JGJ/T341-2014 technical Specification for foam concrete application. If the wet density is too high, continuing to add the foam; if the wet density is too low, the preparation is resumed.
Further, in the step (6), the temperature in the standard curing room is 20 +/-2 ℃, and the relative humidity is more than 95%.
The carbon black-carbon fiber composite wave-absorbing foam concrete prepared by the method has certain wave-absorbing performance and small light weight density, and can reduce the dead weight of a building by about 25% by using the foam concrete on the inner wall and the outer wall of the building without additionally coating a wave-absorbing coating.
Compared with the prior art, the invention has the advantages and beneficial effects that:
(1) the foam concrete prepared greatly reduces the real part of the dielectric constant of the cement due to the introduction of foam, effectively improves the dielectric loss of the cement, and is beneficial to the incident electromagnetic wave to penetrate through the absorber rather than generate poor reflection. The presence of high porosity will provide more space for the propagation of incident electromagnetic waves, which can be confined in internal voids, and then energy can be dissipated and dissipated by multiple scattering.
(2) The nano carbon black and the carbon fiber material are selected for mixing, the fine particle filler has a lubricating effect and a ball effect among fibers during stirring, the rheological property is improved, the problem of thickening of slurry during single mixing of the fillers is well solved, the dispersion of aggregate is promoted to a certain extent, the agglomeration effect is weakened, foams are kept to be uniformly distributed and are not easy to merge, and the stability of a cellular structure is improved.
(3) The two wave absorbers which are uniformly distributed can improve the whole polarization loss and resistance heat loss effects of the hardened composite material, and part of electromagnetic waves are converted into heat energy to be lost in a network formed by overlapping of the disorderly conductive particles.
Drawings
FIG. 1 is a diagram of a sample prepared in accordance with an embodiment of the present invention.
FIG. 2 is a graph showing the flexural strength of the test pieces prepared in the examples of the present invention and the comparative examples.
FIG. 3 is a graph of conductivity and resistivity for samples prepared according to examples of the present invention and comparative examples.
FIG. 4 is a graph showing imaginary parts of dielectric constants of samples prepared in examples of the present invention and comparative examples.
Fig. 5 is a graph showing impedance matching of samples prepared in examples of the present invention and comparative examples.
Fig. 6 is a graph of reflection loss for samples prepared according to examples of the present invention and comparative examples.
Wherein: CB1, CB2, CB1CF0.25, CB1CF0.75 and CB1CF1.5 in fig. 2 to 6 correspond to the samples prepared in comparative example 2, comparative example 3, example 1, example 2 and example 3, respectively.
Detailed Description
The applicant further describes the technical solution of the present invention with reference to specific embodiments, but the scope of the claims of the present invention is not limited to these embodiments.
The following raw materials were used in the respective examples and comparative examples:
nano carbon black: purchased from ultra dense high graphite and carbon Limited, with a particle size of 40 nm;
carbon fiber: the carbon fiber is purchased from Xiamen Kaina graphene technology Co Ltd, and the model is T300 short carbon fiber, the length is 1mm, and the diameter is 7 mu m;
foaming agent: HTW-1 type composite foaming agent, purchased from Hippon Huatai New materials science and technology Co., Ltd;
cement: the cement is 42.5-grade quick-setting and quick-hardening sulphoaluminate cement purchased from Taishan Arctic bear building materials Co.Ltd;
silica fume: from platinum casting materials, Inc. of Henan, SiO 2 ≥98％；
Polycarboxylic acid water reducing agent: purchased from Shanghai minister and promoter chemical technology Co., Ltd, the appearance is white powder, and the water reducing rate is more than or equal to 25 percent;
hydroxypropyl methylcellulose: purchased from Hebei Junjun cellulose factory, is white-like powder in appearance and is easy to dissolve in water.
The following examples and comparative examples used mixers: is a cement mortar mixer, a model jj-5 of a new tin-free instrument and technology company Limited.
It should be noted that:
1. the moulds used for preparing the samples in the embodiment and the comparative example are specially-made metal moulds, the outer diameter is 23.15mm (-0.15mm), the inner diameter is 10.06mm (+0.05mm), the length is 20mm (+/-0.05mm), the ring surface flatness is required to be Ra1.6, and the parallelism of two ring surfaces is required to be 0.05 mm.
2. The wet density of the slurry tested in the inventive examples and comparative examples was performed according to JGJ/T341-2014 foam concrete application Specification.
Example 1: preparation method of carbon black-carbon fiber composite wave-absorbing foam concrete
(1) Weighing 100g of foaming agent, weighing the required water according to the dilution factor of 40 times, and uniformly stirring to obtain a foaming agent solution;
(2) 288g of cement, 3g of nano carbon black and 3g of polycarboxylic acid water reducing agent are respectively weighed and put into a self-sealing bag to be sealed and shaken uniformly, and then pre-physical dispersion is carried out;
(3) weighing 9g of silica fume and 0.75g of carbon fiber, putting into a stirring pot, and slowly stirring for 2min by using a stirrer to perform pre-physical dispersion;
(4) pouring all the dry powder in the step (2) into the stirring pot in the step (3), and slowly stirring for 2 min;
(5) weighing 0.9g of hydroxypropyl methyl cellulose and 150g of water, mixing the two, quickly stirring for 1min to obtain a hydroxypropyl methyl cellulose solution, pouring the solution into the stirring pot in the step (4), slowly stirring for 2min, and quickly stirring for 2 min. Foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, taking 9.6g of foam, quickly adding the foam into a stirring pot, and uniformly stirring to obtain slurry with the wet density of 896g/cm 3 (at 810 g/cm) 3 ～990g/cm 3 Inner, satisfy);
(6) pouring the fresh slurry obtained in the step (5) into a mold for molding, placing the mold into a standard curing room (the temperature is 20 +/-2 ℃, and the relative humidity is more than 95 percent) for curing for 24 hours, taking out the mold for removing the mold, and continuously placing the mold into the curing room for 16 days.
Example 2: preparation method of carbon black-carbon fiber composite wave-absorbing foam concrete
(1) Weighing 100g of foaming agent, weighing the required water according to the dilution multiple of 40 times, and uniformly stirring to obtain a foaming agent solution;
(2) 288g of cement, 3g of nano carbon black and 3g of polycarboxylic acid water reducing agent are respectively weighed and put into a self-sealing bag to be sealed and shaken uniformly, and then pre-physical dispersion is carried out;
(3) weighing 9g of silica fume and 2.25g of carbon fiber, putting into a stirring pot, slowly stirring for 2min by using a stirrer, and performing pre-physical dispersion;
(4) pouring all the dry powder in the step (2) into the stirring pot in the step (3), and slowly stirring for 2 min;
(5) weighing 0.9g of hydroxypropyl methylcellulose and 150g of water, mixing the two, quickly stirring for 1min to obtain a hydroxypropyl methylcellulose solution, pouring the solution into the stirring pot in the step (4),slowly stirring for 2min, and rapidly stirring for 2 min. Foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, taking 8.5g of foam, quickly adding the foam into a stirring pot, uniformly stirring, and measuring the wet density of the slurry at the moment of 916g/cm 3 (at 810 g/cm) 3 ～990g/cm 3 Inner, satisfy);
(6) pouring the fresh slurry obtained in the step (5) into a mold for molding, placing the mold into a standard curing room (the temperature is 20 +/-2 ℃, and the relative humidity is more than 95 percent) for curing for 24 hours, taking out the mold, removing the mold, and continuously placing the mold into the curing room for 16 days.
Example 3: preparation method of carbon black-carbon fiber composite wave-absorbing foam concrete
(1) Weighing 100g of foaming agent, weighing the required water according to the dilution multiple of 40 times, and uniformly stirring to obtain a foaming agent solution;
(2) 288g of cement, 3g of nano carbon black and 3g of polycarboxylic acid water reducing agent are respectively weighed and put into a self-sealing bag to be sealed and shaken uniformly, and then pre-physical dispersion is carried out;
(3) weighing 9g of silica fume and 4.5g of carbon fiber, putting into a stirring pot, and slowly stirring for 2min by using a stirrer to perform pre-physical dispersion;
(4) pouring all the dry powder in the step (2) into the stirring pot in the step (3), and slowly stirring for 2 min;
(5) weighing 0.9g of hydroxypropyl methyl cellulose and 150g of water, mixing the two, quickly stirring for 1min to obtain a hydroxypropyl methyl cellulose solution, pouring the solution into the stirring pot in the step (4), slowly stirring for 2min, and quickly stirring for 2 min. Foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, taking 9.6g of foam, quickly adding the foam into a stirring pot, and uniformly stirring to obtain slurry with the wet density of 908g/cm 3 (at 810 g/cm) 3 ～990g/cm 3 Inner, satisfy);
(6) pouring the fresh slurry obtained in the step (5) into a mold for molding, placing the mold into a standard curing room (the temperature is 20 +/-2 ℃, and the relative humidity is more than 95 percent) for curing for 24 hours, taking out the mold, removing the mold, and continuously placing the mold into the curing room for 16 days.
Comparative example 1: preparation method of carbon black-carbon fiber composite wave-absorbing foam concrete
(1) Weighing 100g of foaming agent, weighing the required water according to the dilution multiple of 40 times, and uniformly stirring to obtain a foaming agent solution;
(2) 288g of cement, 3g of nano carbon black, 3g of polycarboxylic acid water reducing agent, 9g of silica fume and 4.5g of carbon fiber are respectively weighed and put into a self-sealing bag to be sealed and shaken uniformly, namely, pre-physical dispersion is carried out;
(3) pouring all the dry powder in the step (2) into a stirring pot, and slowly stirring for 3min by using a stirrer;
(4) weighing 0.9g of hydroxypropyl methyl cellulose and 150g of water, mixing the hydroxypropyl methyl cellulose and the water for quickly stirring for 1min to obtain a hydroxypropyl methyl cellulose solution, pouring the solution into the stirring pot in the step (3), slowly stirring for 2min, observing the agglomeration of carbon fibers and nano carbon black in ash, allowing the nano carbon black to adsorb more water molecules due to the large specific surface area, gradually increasing the friction force among flocculates, increasing the consistency of cement slurry, ensuring poor flow performance of fresh slurry, thickening the slurry and integrally presenting a coarse state, ensuring that the whole slurry environment is not beneficial to the post-mixing of foam, and continuously and quickly stirring for 2 min.
(5) And (2) foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, adding the required foam, quickly adding the foam into a stirring pot, and stirring, wherein the foam and the slurry cannot be uniformly mixed, the foam cannot be dissolved into the freshly mixed slurry, the defoaming is serious, and the uniform small-hole structure is not favorably formed.
Comparative example 2: preparation method of carbon black-based wave-absorbing foam concrete
(1) Weighing 100g of foaming agent, weighing the required water according to the dilution multiple of 40 times, and uniformly stirring to obtain a foaming agent solution;
(2) 288g of cement, 3g of nano carbon black, 3g of polycarboxylic acid water reducing agent and 9g of silica fume are respectively weighed and put into a self-sealing bag to be sealed and shaken uniformly, namely, pre-physical dispersion is carried out;
(3) pouring all the dry powder in the step (2) into a stirring pot, and slowly stirring for 3min by using a stirrer;
(4) weighing 0.9g of hydroxypropyl methyl cellulose and 150g of water, mixing the two, quickly stirring for 1min to obtain a hydroxypropyl methyl cellulose solution, pouring the solution into the stirring pot in the step (3), slowly stirring for 2min, and quickly stirring for 2 min. Using a foaming machine to mix the foaming agent solution obtained in the step (1) during stirringFoaming, namely taking 9.4g of foam, quickly adding the foam into a stirring pot, and uniformly stirring to obtain slurry, wherein the wet density of the slurry is 904g/cm 3 (at 810 g/cm) 3 ～990g/cm 3 Inner, satisfy);
(5) pouring the fresh slurry obtained in the step (4) into a mold for molding, placing the mold into a standard curing room (the temperature is 20 +/-2 ℃, and the relative humidity is more than 95 percent) for curing for 24 hours, taking out the mold, removing the mold, and continuously placing the mold into the curing room for 16 days.
Comparative example 3: preparation method of carbon black-based wave-absorbing foam concrete
(1) Weighing 100g of foaming agent, weighing the required water according to the dilution multiple of 40 times, and uniformly stirring to obtain a foaming agent solution;
(2) respectively weighing 285g of cement, 6g of nano carbon black, 3g of polycarboxylic acid water reducing agent and 9g of silica fume, putting into a self-sealing bag, sealing and shaking uniformly, namely performing pre-physical dispersion;
(3) pouring all the dry powder in the step (2) into a stirring pot, and slowly stirring for 3min by using a stirrer;
(4) weighing 0.9g of hydroxypropyl methyl cellulose and 150g of water, mixing the two, quickly stirring for 1min to obtain a hydroxypropyl methyl cellulose solution, pouring the solution into the stirring pot in the step (3), slowly stirring for 2min, and quickly stirring for 2 min. Foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, taking 9.1g of foam, quickly adding the foam into a stirring pot, and uniformly stirring to obtain slurry with the wet density of 912g/cm 3 (at 810 g/cm) 3 ～990g/cm 3 Inner, satisfy);
(5) pouring the fresh slurry obtained in the step (4) into a mold for molding, placing the mold into a standard curing room (the temperature is 20 +/-2 ℃, and the relative humidity is more than 95 percent) for curing for 24 hours, taking out the mold, removing the mold, and continuously placing the mold into the curing room for 16 days.
Comparative example 4: preparation method of carbon black-carbon fiber composite wave-absorbing foam concrete
The applicant tries to further prepare the cement-based wave-absorbing foam concrete from the lower slab slurry in the example 1 of the prior art (CN109293310A, a double-layer cement-based wave-absorbing slab doped with graphene nano-sheets and a preparation method thereof). The preparation method comprises the following steps:
weighing 100g of foaming agent, weighing the required water according to the dilution multiple of 40 times, and uniformly stirring to obtain a foaming agent solution; preparing a lower layer slurry according to CN109293310A example 1 step (1), foaming the foaming agent solution by using a foaming machine during stirring, taking 8.5g of foam, quickly adding the foam into a stirring pot for stirring, and measuring the wet density of the slurry at the moment to be more than 990g/cm 3 (ii) a Because the mixing amount of the carbon black reaches 6% of the mass of the cement, and the mass of the water reducing agent is less, the slurry has poor fluidity, the defoaming is serious when the slurry is fused with the foam, and the slurry is too thick and cannot wrap more foam, so that the need of further adding the foam is avoided.
The applicant further tried to prepare the cement-based wave-absorbing foam concrete by adopting a mixing mode of lower plate slurry in the prior art (CN109293310A, a double-layer cement-based wave-absorbing plate doped with graphene nano sheets and a preparation method thereof). The preparation method comprises the following steps:
(1) weighing 100g of foaming agent, weighing the required water according to the dilution multiple of 40 times, and uniformly stirring to obtain a foaming agent solution;
(2) adding 100g of water with the temperature of 60 ℃ into a beaker, slowly adding 0.9g of hydroxypropyl methyl cellulose into the water, stirring until the hydroxypropyl methyl cellulose is fully dissolved, then adding 2.25g of carbon fiber into the beaker, and uniformly stirring the mixture to form a carbon fiber dispersion liquid for later use; 288g of cement and 9g of silica fume are respectively poured into a stirring pot, after stirring uniformly, 3g of nano carbon black and carbon fiber dispersion liquid are added, stirring uniformly again, finally, 3g of polycarboxylic acid water reducing agent and 50g of water are added, stirring is carried out at a low speed for 2.5min, stopping stirring for 20s, and stirring at a high speed for 2.5 min;
(3) foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, taking 9.5g of foam, quickly adding the foam into a stirring pot for stirring, and measuring the wet density of the slurry at the moment to be more than 990g/cm 3 Too thick slurry can not wrap more foam, and too much foam is added to cause water-cement ratio deviation, so that the foam is not added continuously.
The test simulation was performed on the samples having a thickness of about 10mm prepared in examples 1 to 3 and comparative examples 2 to 3 by the coaxial line transmission reflection method under the electromagnetic wave reflectance of 0.1 to 5GHz, and the results are shown in table 1. Wherein: the testing instrument is a vector network analyzer of a middle electrical department instrument and meter company Limited, a COTRLD105V01 clamp of the middle electrical department is adopted as the clamp, the frequency band of the clamp is 0.1-5 GHz, Agilent Connection Expert is used as testing software, and the reflectivity and the wave absorbing performance of the testing instrument are calculated according to a transmission line theory.
The flexural strength is determined according to the specification GB/T17671-1999 method for testing the strength of cement mortar.
The conductivity of the test block was measured using a digital bridge tester manufactured by Jiangsu Yong. When a test block is poured, a copper net is inserted into the unset slurry, the copper net is vertically inserted into the slurry as much as possible, the insertion depths of the two sides are kept consistent, and the test error is reduced. The sizes of the copper meshes are 3 multiplied by 4cm, the resistance R of the test block is measured by an instrument, each group is tested for 3 times, the average value is taken, and the resistivity rho is obtained according to the formula 1, wherein S is the insertion area of the copper meshes, and L is the distance between the two copper meshes.
Formula 1:
TABLE 1
The reflectivity < -10dB bandwidth means that the material can effectively absorb 90% of the electromagnetic wave when the reflection loss is lower than 10 dB. Z in /Z 0 Representing the ratio of the input wave impedance to the air impedance, the closer the ratio is to 1 the better.
Claims (10)
1. The carbon black-carbon fiber composite wave-absorbing foam concrete is characterized in that the concrete is prepared by mixing a wave-absorbing material and a foaming agent to prepare slurry and further maintaining the slurry; the wet density of the slurry is (900 +/-90) g/cm 3 ；
The wave-absorbing material is prepared from the following raw materials: ash, additive and water; wherein the ash body consists of cement, silica fume and nano carbon black; the additive is composed of methyl cellulose, a polycarboxylic acid water reducing agent and carbon fibers;
the wave-absorbing material comprises the following components in parts by weight: cement accounts for 96wt% of the ash body, silica fume accounts for 3wt% of the ash body, and nano carbon black accounts for 1wt% of the ash body; the methyl cellulose accounts for 0.3wt% of the ash body, the polycarboxylic acid water reducing agent accounts for 1.0wt% of the ash body, the carbon fiber accounts for 0.25wt% -1.5 wt% of the ash body, and the water-cement ratio is 0.5;
the foaming agent is a physical foaming agent.
2. The carbon black-carbon fiber composite wave-absorbing foam concrete according to claim 1, wherein the carbon fibers account for 0.75wt% to 1.5wt% of the ash.
3. The carbon black-carbon fiber composite wave-absorbing foam concrete according to claim 1, wherein the carbon fibers account for 0.75wt% to 1.0wt% of the ash.
4. The carbon black-carbon fiber composite wave-absorbing foam concrete according to any one of claims 1 to 3, wherein the nano carbon black: the grain size is less than or equal to 40 nm; the carbon fibers are chopped carbon fibers, the length of the carbon fibers is 0.7-1.5mm, and the diameter of the carbon fibers is 5-8 mu m.
5. The carbon black-carbon fiber composite wave-absorbing foam concrete according to any one of claims 1 to 3, characterized in that the carbon fibers are chopped carbon fibers, and have a length of 1mm and a diameter of 7 μm.
6. The carbon black-carbon fiber composite wave-absorbing foam concrete according to any one of claims 1 to 3, wherein the cement is a fast setting and hardening sulphoaluminate cement.
7. The carbon black-carbon fiber composite wave-absorbing foam concrete according to any one of claims 1 to 3, wherein SiO is contained in the silica fume 2 More than or equal to 98 percent; the methyl cellulose is hydroxypropyl methyl cellulose; the water reducing rate of the polycarboxylate superplasticizer is more than or equal to 25 percent.
8. The carbon black-carbon fiber composite wave-absorbing foam concrete according to any one of claims 1 to 3, characterized in that the foaming agent is a HTW-1 type composite foaming agent.
9. The method for preparing carbon black-carbon fiber composite wave-absorbing foam concrete according to any one of claims 1 to 8, characterized by comprising the steps of:
(1) weighing foaming agent, weighing the required water according to the corresponding dilution times, and uniformly stirring to obtain foaming agent solution;
(2) respectively weighing cement, nano carbon black and a polycarboxylate superplasticizer, putting the materials into a self-sealing bag, sealing and shaking up, namely performing pre-physical dispersion;
(3) weighing silica fume and carbon fiber, putting into a stirring pot, slowly stirring for 2-3 min by using a stirrer, and performing pre-physical dispersion;
(4) pouring all the dry powder in the step (2) into the stirring pot in the step (3), and slowly stirring for 2-3 min;
(5) weighing methyl cellulose and water, mixing the methyl cellulose and the water, quickly stirring for 1min to obtain a methyl cellulose solution, pouring the obtained methyl cellulose solution into the stirring pot in the step (4), slowly stirring for 2-3 min, and quickly stirring for 2-3 min; foaming the foaming agent solution obtained in the step (1) by using a foaming machine during stirring, taking foam, quickly adding the foam into a stirring pot, and uniformly stirring to ensure that the wet density of the slurry is (900 +/-90) g/cm 3 ；
(6) Pouring the fresh slurry obtained in the step (5) into a mold for molding, placing the mold into a standard curing room for curing for 16-24h, taking out the mold for removing, and continuing placing the mold into the standard curing room for curing to the applicable age.
10. The method of claim 9, wherein the blowing agent in step (1) is a HTW-1 type composite blowing agent, and the dilution ratio is 40 times.
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